River Boat Design

[mrdancer]

I need a boat for working on sandbars in the river. The boat needs to be lightweight (so we can push it off of submerged sandbars), able to run in shallow water (so we can get close to sandbars) and able to carry at least five people. Here are some thoughts I have... :D

1. Overall design will be a jon boat due to shallow water capabilities and utility.

2. Long & skinny. I'm thinking 25 feet long and 5 feet wide. Length is good because we can get the bow up on a sandbar and still have the motor out there in deeper water. It also helps for pushing the boat off of a submerged sandbar, e.g. - shift the cargo to the deepwater end, etc. I'm going with a narrow design as that will help keep weight down.

3. Flat bottom for maximum shallow-water capability. I'd like somewhat of a modified-V bow for cutting waves. I know it will ride rough in a chop, but I plan to combat that with soft seats and cushy pads to stand on.

4. Tunnel-hull, for shallow-water capability. Tunnel would be about eight feet long for a 25-foot boat, about 14 inches wide and 6 inches deep. It will be either five-sided or round.

5. Engine: I'm used to 60hp motors, but I'm not sure if that's enough oomph to plane a 25'x5' boat easily, especially with five people aboard. Yamaha makes a 90hp 2-stroke that is relatively lightweight, so may go with that. Motor will be mounted on a hydraulic jack plate to maximize tunnel effectiveness. Will need a good cupped four-blade stainless to get a good bite on the tunnel water.

6. Boat will have an elevated center console, maybe a foot or two higher than a typical center console. This will provide maximum visibility for the captain and aid in avoiding those phantom submerged sandbars. Nothing quite as drastic as the tower boats that are running the flats, though. Console will also be mounted a little further forward to help the boat run flat at slow planing speeds.

7. Floatation pods at the stern. Help to keep the boat running flat.

8. Trim tabs. A lot of the best flats boats use them, and they swear by them, especially for getting up and running in shallow waters. Would help provide a drier ride in a chop, also.

9. Sides of boat will be around eighteen inches toward the stern, and twenty-four inches toward the bow (hoping to provide for a little drier ride this way, while keeping weight down).

That's most of what I can think of off the top of my head. Any glaring omissions, comments, etc.? :confused:

[icetreader]

mrdancer,

Looks like a nice plan.

Why 5 ft wide? (why not more and why not less?)
What are you planning to achieve with the tunnel?

[longliner45]

I used to own a 24 ft lapstreak great lakes riverboat it was designed by the sandusky boat works in sandusky ohio she was 12 ft wide and24 ft long she didnt have a screw in her all made with dowes. engine was 292 chevy;forget 5ft wide the first barge that goes by ya will sink ya ,,,,,,,what do you whan the boat for?

[tom28571]

A 25' by 5' lightweight flat bottom boat with five people moving around doesn't sound too good to me. Not real stable and there is no compelling reason to go flat. With 90 hp on the stern, I would not let anyone I particularly like go with you and three others in that boat. I'd go beamier at about 6.5' to 7' with some bow shape and the tunnel you like. 50 hp should be more than adequate to plane a decently designed boat to suit you. Even 25 hp might do it.

One boat that comes to mind is Atkins Rescue Minor, although it's a bit small at 19'. http://www.boat-links.com/Atkinco/Utilities/RescueMinor.html This is not a planing boat but should run in the high teens with not so much power. I see no reason why it could not be made larger with a little design work.

[mrdancer]

I chose five feet width as a compromise. Narrower could lead to stability problems and wider may unnecessarily increase weight. We currently have a jon boat that is 19 feet long and 54 inches wide. With a 40hp 2-stroke Evinrude, it planes easily and runs stable with five people aboard, as long as the water is smooth. With a little chop on the water, it becomes a wet ride (console mounted forward, 18-inch sides). It is a riveted single hull design, and is going on 15 years old, leaking a little and starting to fall apart in general. We'd like to upgrade to a little more capacity and a drier ride.

This is a large shallow river we are working on (upper Missouri River). Typically the river may be anywhere from a half-mile to a mile wide, and most of it less than a foot deep, consisting of shallow, braided channels with an occasional 20-foot-plus deep channel (thalweg). I say occasional, because in some places the thalweg disappears completely. No barge traffic on this river! Current is typically around 3mph in the main channels. Water is often turbid, so sandbars more than a few inches below the surface are often hard to spot, hence the ease of running up on one, then having to manhandle to boat off of it. This is a National Recreational River, so airboats are not allowed, nor are jet skis. Jet drive outboards have been tried in the past, but the fine suspended sands in the water eat up the impellers quickly and they become a maintenance nightmare.

I'd like to stick with a 60hp four-stroke if it will plane the boat easily with five people aboard. If that's not enough power, I think Yammie makes the lightest 90hp two-stroke outboard (only 24 lbs heavier than a 60hp four-stroke). We went with Yammies because recent Mercs we had would keep plugging up with sand.

The reason for the tunnel is for getting into the shallow water. I know the tunnel hulls don't handle very well and some buoyancy is lost; however, we are willing to give that up to get the extra inch or two of shallow-running capability. We would also rather have a 10-15 year life span single hull that weighs 500lbs than a 30 year life span double hull that weighs 900lbs.

[safewalrus]

Just one small problem as I can see! Freeboard needs to be as low as possible, it sounds as if your going to be getting in and out of the boat fairly regularly! to shove off etc! With that narrow beam each time you try to step over a high bulwark your going to tip it! As it tips it keeps going, and gone - three knots current that everything you've got disappearing down river quicker than you can run! Plus it 'only needs a cup of water to drown' in if somebody goes in awkward! other than that can't see much of a problem - go build your boat!

[tom28571]

You should reconsider the beam issue. Adding to the beam is the most effective way to increase stability, load carrying and easy planing with minimum hull weight. I built a cruising powerboat with a hull weight of about 1900 lbs, LOA is 24', beam is 8' and a hull draft of nominal 7 to 8 inches. With 6 adults aboard she planes easily from about 11mph up to a max speed of over 20 mph and is powered by a Yamaha T50. Don't understand the need for so much power.

Robb Whites version of the Rescue Minor can run in 6" of water. Look at the impressive photos in: http://www.robbwhite.com/rescue.minor.html

I don't think long and skinny is the best way to reach all your goals. No, that's not right. I'm positive that long and skinny is not the best way to go.

[tom kane]

As a life time shallow water boatie I believe that you must have the necessary amount of buoyancy to keep your total load on top of the water at all times,and a very shallow planing angle so the stern of the boat does not drop to much when starting to go over the hump or in shallow water.A narrow beam does not give a lot of buoyancy.A V hull with a 6 inch deadrise 20 feet by 6 ft 6 in beam should support five people luggage and a large outboard with a draught of 4 to 6 inches if you have not external keel (tripple keelson).Any tunnels added would reduce buoyancy in an important most area.A hull with a nose down attitude at rest that levels up with a few RPM on helps to navigate the shallows better,keeps the stern up.A flat bottom boat does not necessarily meam a shallow draught if there is not enough buoyancy to carry the weight.The outboard motor needs to be able to rise automatically to the surface by a pivoting mounting like an rise and fall outboard bracket.The motor will push it`s self up on striking the bottom and pivot back as thrust is lost.Photos in my photo album give some idea of shallow water boating with a pivoting drive inboard.

www.boatdesign.net/gallery/showgallery.php/cat/500/page/2/ppuser/1988

[mrdancer]

Thank you all for the responses. As I've said, we have a 19-foot jon with a 54-inch bottom width (around 60-inch top width), and it seems to be plenty stable for us, which is why I thought maybe I could add six more feet of length along with 6 inches width and still keep the stability. I will think more about going to a 72-inch width. Remember, we'll probably be pulling this thing off of submerged sandbars many times, so I want something that is relatively lightweight and flat-bottomed so it doesn't hang up or get sucked down in the silty sandy substrate. Our best boats right now have about a 6-degree deadrise at the bow tapering to a 0-degree deadrise about 1/4 to 1/3 of the way back to the stern, and they are single-hull riveted models (I understand, though, that a high-quality welded boat may weigh less than a riveted model). Fiberglass won't last long in the environment we run these boats in (sand, gravel, snags and other hazards).

Tom, I saw your pics of the pivotal drive, but no real good photos of how the drive actually works. How is the engine-cooling accomplished without plugging up the cooling intakes with mud/silt/sand? Is it a closed-loop cooling system with air-to-water heat exchanger? That would be too heavy/complicated for our purposes. We have used the GoDevil-type motors (air-cooled) and boats here on the river, but those boats are undersized and slow, and still have problems in the sand. We've also tried the jets, and keep going back to the outboard prop drive as the most reliable low-maintenance system, as long as we can keep silt/sand out of the cooling system. We typically run in 90-degree ambient temps with water temps approaching 80 degrees, so overheating can be a problem if the cooling system isn't up to par.

I've attached a few photos to give you an idea of what we are working in. Shallow water with a lot of submerged sandbars that shift around constantly, and water level varies quite a bit to add to the problem. Deeper water comes in the form of braided channels with an occasional thalweg, making navigation rather tricky, especially when the water is turbid or skies are cloudy.

Perhaps a boat such as the flats cat www.flatscat.com would serve our purposes just as well? :confused: I talked with the owner and he says that they build them in aluminum also.

[kach22i]

May I suggest a hovercraft?

[mrdancer]

May I suggest a hovercraft?


Poor capacity/power ratio, high maintenance. They are considered airboats and thus are not legal to run on this stretch of the river (considered a National Park).

[tom kane]

Like you we have tried all the propulsion methods,including cushion craft for water ways similar to yours.Outboard are easier for most people.but put the weight where it is not wanted.The trimable shaft fitted to a boat is as light as you can get with any type of motor,closed fluid cooled (quiet) or air cooled.There are many ways to set it up and the main advantage is that the skeg and shaft slide up with a cam like action and the operator does not need to control it as it follows the bottom and moves up and down depending on the depth of water.Good propeller protection can be added.

[lewisboats]

Sorta like this? (disregard the waterline, I didn't bother to adjust it)



Steve

[JEM]

You won't displace as much with a tunnel as you would with a flat bottom.

To get the shallow water ability, couldn't you just set the motor on a jack plate or something?

[mrdancer]

Like you we have tried all the propulsion methods,including cushion craft for water ways similar to yours.Outboard are easier for most people.but put the weight where it is not wanted.The trimable shaft fitted to a boat is as light as you can get with any type of motor,closed fluid cooled (quiet) or air cooled.There are many ways to set it up and the main advantage is that the skeg and shaft slide up with a cam like action and the operator does not need to control it as it follows the bottom and moves up and down depending on the depth of water.Good propeller protection can be added.

I'm still not sure what advantage your system has, Tom. I can see where it might protect the motor (and transom to a degree) if one should hit an underwater obstruction, but otherwise I don't see what advantage it has over a hydraulic jack plate for shallow water running. We are limited to running outboards, which have open cooling systems.:(

[mrdancer]

Sorta like this? (disregard the waterline, I didn't bother to adjust it)

Yep, that's almost exactly what I'm talking about! :)

[mrdancer]

You won't displace as much with a tunnel as you would with a flat bottom.

To get the shallow water ability, couldn't you just set the motor on a jack plate or something?

Yes, I realize the buoyancy would be less with the tunnel, but the tunnel will still allow shallower running. Every inch makes a huge difference when the water gets skinny. Some of the buoyancy/displacement can be overcome with flotation pods on the stern, and trim tabs can also assist in getting the boat up on plane (see original post). I've incorporated a hydraulic jack plate in the design to take full advantage of the tunnel; otherwise, without a tunnel, much of the jack plate is wasted.

[lewisboats]

I took the liberty of adding a tunnel, and a couple of bouyancy chambers aft of the motor mount. 1: These will support the motor 2: they will cut down on spray (hopefully) from the shallow prop and 3: will allow easier entering and exiting of the boat by having a folding ladder on one or both sides. I stuck a center console on and added the Specs in a .txt file too.

steve

[kach22i]

Poor capacity/power ratio, high maintenance. They are considered airboats and thus are not legal to run on this stretch of the river (considered a National Park).
National Park status excludes hovercraft because hovercraft can go where other craft dare not tread. The park system did not want to become obligated to rescuing stranded hovercraft, as that would require purchase/use of yet more hovercraft for the rescue.

Cell phones have increased the obligation to rescue people, before cell phones the Park system would recover dead bodies from the river (flash flood common thing certain times of year) as much as rescue live people.

I'm not sure what your payload requirement is - would 700-800 lbs be anywhere near enough (4-5 people)?

For those who venture into the back rivers of Alaska where dependablity of automobile engines and low fuel consumption is important you might want to click one of the links below.

http://members.aol.com/sevtec/sev/skmr.html

Geoduck:
http://members.aol.com/hovtec/hover/GEO.html

Note-1: I am not associated with this maker, but do admire the design (low noise and takes on big 15 foot waves).

Note-2: My hovercraft skirt lasted 15 years (different craft) - not too shabby.

[kach22i]

I just though I should mention the elevated center console model Sevtec - hope you don't mind the hijacking.;)

Link:
http://members.aol.com/sevtec/sev/CUST.html

http://members.aol.com/sevtec/sev/KCFD4.jpg

http://members.aol.com/sevtec/sev/KCFDCOMP.jpg

Good luck with your boat design - it's looking nice so far.

[kach22i]

I wonder what one of these would go for at an surplus auction.

http://www.defence.gov.au/dmo/news/ontarget/sept05/images/nb4_bepb0101.jpg

From here:
http://www.defence.gov.au/dmo/news/ontarget/sept05/nb4.cfm
A Bridge Erection Propulsion Boat travelling in shallow water on the Hastings River, adjacent to the Birdon Marine facility at Port Macquarie.

Also found this:

http://www.hammondfishing.com/jims-boat-kf-tourney-03-cropped-web-format.jpg
http://www.hammondfishing.com/ponte-vedra.htm
27 foot skiff (Capt Jim Hammond's Boat)
Shallow Draft, High Sides.
This boat is 27 feet long and 9 feet wide
The most stable backwater / river boat you will ever fish in.
Top of the line 36 volt trolling motor and electronics

[mrdancer]

I took the liberty of adding a tunnel, and a couple of bouyancy chambers aft of the motor mount. 1: These will support the motor 2: they will cut down on spray (hopefully) from the shallow prop and 3: will allow easier entering and exiting of the boat by having a folding ladder on one or both sides. I stuck a center console on and added the Specs in a .txt file too.

steve

Yep, that boat is almost perfect! That's what I'm looking for.

I'd maybe make the tunnel a little narrower - I think 14 inches would probably be wide enough. I'm also thinking the tunnel should be as wide at the front as at the rear, maybe even slightly wider...

[mrdancer]

I wonder what one of these would go for at an surplus auction.


I've seen those National Guard Bridging Unit jet boats in action. A little too big and heavy for what I need, plus it takes an experienced crew just to launch and load the thing! :eek: Interesting concept, though!


Also found this:


I've actually been on a Carolina Skiff before, though not one that big. They seem to be a pretty average boat, as far as shallow draft boats go. There are boats out there that go shallower (try googling for "flats boat" to get an idea of what they use in skinny water on the coast to get to redfish). Plus, I don't believe they build the CS in aluminum. :confused:

[srwshooter]

http://i10.photobucket.com/albums/a126/srwshooter/rhino.jpgjust get one of these with a jet.......you can get them 22ft. and 72 wide

[mrdancer]

http://i10.photobucket.com/albums/a126/srwshooter/rhino.jpgjust get one of these with a jet.......you can get them 22ft. and 72 wide

Once again, jet motors will not work in this river. There is a LOT of fine suspended silts and sugar sands that will eat up a jet impeller rather quickly (unless it's one of them big ol' reversible Hamilton jets, maybe...)

[BOATMIK]

Go simple rather than complex.

forget the tunnel - the boat will only be a few inches deep unless you make the boat heavy and complicated like some of the pics above.

It is likely the tunnel will take the prop above the static waterline, so it will just suck air - particularly if you have to reverse thrust at any point. An outboard is the simplest solution - just swings up.

5ft beam indicates something simple, relatively light. This also indicates a minimal need for power.

http://www.alaska.net/~fritzf/Boats/Sneakeasy/picnic3thumb.jpg

The one in the pic is to carry low loads but if you look at the page reference below it will show some other versions of the same concept. These boats run well with heavy loads anyhow.

A 10hp outboard would drive a simple box hullform of those proportions at a cruising speed of over 10 knots with a few extra in reserve. this is the benefit of the narrow beam, generous length and light displacement.

Box hullform gives good static stability. If run very fast and turned quick such boats can trip and roll.

Seakeeping is good providing that the hull bridges several waves at once. If it starts climbing up the face of waves and dropping off the top it will knock your fillings out if you do it at any sort of speed.

Phil Bolger had his IDAHO - it is a bit longer than you are talking about but the beam is in your range He has designed quite a few boats of this concept and they work well - I have used them a fair bit and have drawn up a similar boat.

Some examples ...

http://www.alaska.net/~fritzf/Boats/Sneakeasy/Sneakeasy.htm

Some commentary on the type of boat (mine) including how they actually go in real water.
http://members.ozemail.com.au/~storerm/Dayboat/Dayboat_Launch.html

Michael Storer

[sheetal]

where r u frm?

[kach22i]

Sounds like we are going back in time.

http://www2.richland2.org/rce/transpor.htm

Most cities have rivers going through them, populated and developed long before dams bocked the river, highways went around or through them and airports connected them to the rest of the world.

I live in Ann Arbor Michigan - home of the University of Michigan, back in the 1800's the Huron River was used by over 100 foot long "Cargo Canoes" to help supply the growing city. I have seen the pictures of these cargo canoes because I've done some historic preservation work as an architect.

They really piled high the cargo, and there were lots of them. These boats were different than the cargo barges of the Erie cannel.

[JEM]

mrdancer,

Are you looking to build this or purchase something that is already made?

[longliner45]

what sea arc? they make a big ass johnboat,Pics look neet (where is that) ?

[kach22i]

what sea arc? they make a big ass johnboat,Pics look neet (where is that) ?
You mean Sea Ark?

http://www.seaarkboats.com/

http://www.seaarkboats.com/images/main/seaark_main_model_nav_08a.jpg

[Gilbert]

I saw long narrow vessels in use in Southeastern Alaska by natives that seem like they would be suitable for your purposes.
My intuitive guess was that their boats were reinterpretations of their carved from log canoes after the introduction of the sawmill and nail technology.
The bottoms of these boats were flat and made of three twelve inch wide boards. The overall length of the boats were 30 to 40 feet. The sides were made of two planks and sloped about a 2 to 1 ratio. I don't recall the width of the side planks but if they were not twelve inches they were probably very close to that. It is notable that there were no but splices in the planks. Those were the days! This would make these boats about 5 feet wide. And let me tell you there was no stability problem. And they used the biggest outboards they could get or afford and they ran really well and were fast for the power. This was in 1960 so they were not using 225 Hondas. It was more like 50 or 60 OMCs or Mercs. The bottom curved up some at the bow and the sides curved in some too but they had a pram or transom bow depending on how you want to describe it.
I just thought this might be interesting to add here.

[kach22i]

I saw long narrow vessels in use in Southeastern Alaska by natives that seem like they would be suitable for your purposes.
I did a goole search using some of your terms. I found something called a "Drift Boat", although not what you described - I thought it was interesting.

http://images.google.com/images?svnum=10&hl=en&lr=&safe=off&q=drift+boat&btnG=Search

http://www.boating.co.nz/yarns/DRIFTER4.jpg

http://loganet.net/dougsguideservice/report/hello/443833/640/IMG_0720-2005.08.03-20.23.41.jpg

[oneuglyboat]

your description of what you are using the boat for would fit our road hog 20-22 almost to a tee. its 8.5 wide and draws less than 6 inches of water. oneuglyboat.com harold

[kach22i]

fit our road hog ............. oneuglyboat.com harold
Cool and Popeye seems to like it too.:D

I think this is the design he started looking for.:cool:

[oneuglyboat]

the beauty of this aluminum boat is its strenght and rugged construction, plus the low profile in the water. the side hulls are also full of foam for unsinkable floatation. you can cram it up on the beach or shore and not worry about damaging the hulls. then you can step 17" down to the ground. we have designed several for people who want an ATF and ramp down off the bow for exploring islands or inaccessable areas. it has a lot of load carrying capacity for the 4 wheeler. in fact, i have designed the boat in 24' so that it can carry 2 ATVs

[kach22i]

the side hulls are also full of foam for unsinkable floatation.
I saw in the construction photos sheets of extruded polystyreen (guessing) placed into the sponson. Do you spray any expandable foam in there or do the sheets just rattle around unsecured? Better than the milk jugs I've seen in some homemade hovercraft.;)

[kach22i]

This looks interesting.
http://www.working-boats.co.uk/5.4m_02.jpg

Although I think it may need at least a couple of feet of water to operate in.

Link:
http://www.working-boats.co.uk/WorkstarLC.html

[kach22i]

http://www.aliboats.co.za/images/bargespic10.jpg
http://www.aliboats.co.za/barges.htm

Could prove to be useful.

[Guillermo]

Maybe this propulsion system can also be interesting:
http://www.swordmarine.com/
You need at least 5º slope in the bottom at stern to mount the JetPac.

[kach22i]

http://www.cslpublishingltd.co.uk/news/home_pop.php?id=140
http://www.cslpublishingltd.co.uk/news/pictures/amphibious.jpg

[Wellydeckhand]

Mmmm......... Nice idea...... buying list for next christmas:d

[safewalrus]

Not as good as a nice log kumpit are they Welly?

[Wellydeckhand]

Not as good as a nice log kumpit are they Welly?

Well...... Log get rot:eek: :eek: :eek: ......... It a matter of driving one of this babe in the river and showing off to one of the Haji:D :D before they really know what they missed up in life........ most of them are still stiff neck about outboat engine...........:D :D :D :D :D

I know the American keep compaining about Asian buying off China engine..... but then the manufacture in American didnt get their feet wet by touring with engine demo or boat sample to the people that are loaded and bored to death with kayak and tied logs.....................in this part of the god forsaken world:eek: :eek: :eek: :p (In a matter of speech)........................?yes?.....?Si?:D :D :D :D :D

[messabout]

Long skinny boats are far more sensible for your application. Five foot beam on a flat bottom has entirely enough stability for sober occupants. Long narrow boats make the transition to planing mode smoothly. Short fat ones squat. Your design will ride better than any chubby boat. See Dave Gerr " The Nature of Boats" for a convincing endorsement of long narrow.

Work boats all over the world have used the long narrow pattern for hundreds of years. Think Amazon water transport. South east Asian, etc. You wont need a gob of power or cupped props or any of that trendy stuff either. Check out Bolgers' Sneakeasy design. Thats a 26'6 x 4'3 flat bottomed deal that goes fast with little power. Sneakeasy is not inclined to capsize as the wide boat guys will have it. Consult also, Tom Firth Jones "Low Resistance Boats".

You might consider a dragon tail power unit. Reliable, versatile, practical, thrives in mud, weeds, and other unfavorable surroundings. If air cooled you wont have to replace sand eroded water pumps. O.K. so those things are ugly and weird looking. But they work well.

Gene

[Wellydeckhand]

Mmmm...... of course what u say is right........ i would try to post some traditional cargo boat and dingy......... and **** engine they drive.

The light narrow hull really need miniture engine with long rod to drive. We call it TING-TING.... dont know what the western world called that.

:):):)

[safewalrus]

Wellydeck reminds me of some small experience with long thin boats! His part of the world, locals used long (and I mean long) boats with narrow hulls and thumping great outboards on the back (actually by todays standards they're not all that big but.....) to smuggle cigarettes (and terrorists)! Worked fantastically - the only thing we had to catch 'em were bullets (thing is we had lot's of them)! wern't much good in a chop, but being the tropics it either was flat or horrid (and nobody but the stupid 'round eyes' goes out in **** weather!) and of course they had the speed to get out of trouble quickly (or up the nearest beach)

[Wellydeckhand]

Huh........ Round eyes? U wanna explain it clearer? :):):)

[safewalrus]

Westerners Welly -Us lot, the white(ish)man!

[Wellydeckhand]

Mmmmm........... white eyes walrus.......lolol:D:D:D

[safewalrus]

Yes mate wide legged and eyeless!

[kach22i]

Close to the original request.

http://www.blazerjetboats.com/gallery3.htm

http://www.blazerjetboats.com/6-inches-of-waterlg.jpg